Taking the heat: WAX GC columns

To analyze challenging analytes, your GC or GC/MS system must have the sensitivity to deliver reproducible qualitative and quantitative results.

GC columns based on a 100 percent polyethylene glycol (PEG) stationary phase can be used for a wide variety of applications. These include industrial chemicals, pharmaceutical raw materials, alcoholic beverages, flavors, and fragrances.

Despite their wide range of applications, the columns, also known as WAX columns, typically have lower maximum operating temperatures than nonpolar columns. Heating a standard WAX column above its maximum operating temperature of 260 °C (to ensure that heavy compounds elute from the column to prevent ghost peaks, for example, or to increase reproducibility), damages the stationary phase.

Exceeding the maximum temperature leads to issues such as decreased thermal stability, which reduces the potential range of applications that the columns could be used for. Other problems include elevated column bleed and shorter column lifetime.

Extending heat limits for breakthrough results

Agilent has the ideal solution: its innovative Agilent J&W DB-HeavyWAX GC columns have an improved stationary phase that enables an extended temperature limit of up to 280 °C isothermal and 290 °C programmed. The columns also have improved thermal stability, increasing injection-to-injection reproducibility, and therefore offer a wider application range.

Excellent thermal stability

Agilent scientists compared a commercially available WAX column (Figure 1) to Agilent J&W DB-HeavyWAX (Figure 2) using 100 ppm standard of BTEX over a period of 100 hours operating at 280°C. The graphs below show the results.

This commercially available WAX column, when used above its maximum temperature limit of 250 °C, immediately shows signs of retention time shifting. During 50 hours at 280 °C, the shift in retention time changes from slight to significant

Even after 100 hours of use at 280 °C, Agilent J&W DB-HeavyWAX columns show minimal retention time shift.

Ultralow bleed

Traditional WAX GC columns exhibit high bleed above their maximum temperature limits. Figure 3 shows that after 100 hours at high temperatures (280 °C), bleed of the Agilent J&W DB-HeavyWAX column is still less than 10 pA. Meanwhile, two commercially available WAX columns have column bleed levels between 50 and 60 pA.

Bleed profiles for commercially available WAX columns and Agilent J&W DB-HeavyWAX over 100 hours of use at 280 °C

The Agilent advantage

The Agilent J&W DB-HeavyWAX column provides an increased maximum temperature range. It guarantees thermal stability at high temperatures for increased analyte range and better column-to-column reproducibility. Run times can be up to 20% quicker, and there is low bleed, even at the highest temperatures.